In order to provide a wireless channel to a Mobile Station (MS) located in a cell edge or a shadow area, a wireless communication system provides a relay service using a Relay Station (RS). For example, the wireless communication system relays data transmitted/received between a Base Station (BS) and the MS, using the RS as illustrated in FIG. 1.
FIG. 1 illustrates a construction of a relay wireless communication system.
As illustrated in FIG. 1, the wireless communication system includes a BS 100, an RS 110, an MS1 120, and an MS2 130.
The BS 100 performs direct communication with the MS1 120 located in a service area.
The BS 100 performs communication with the MS2 130 located outside the service area, using the RS 110. That is, the BS 100 uses the RS 110 to provide a good wireless channel to an MS that has a poor channel state due to being either located outside a service area or located in a shadow area where a screening phenomenon is caused by a building and such.
When providing a relay service as above, a wireless communication system provides the relay service using a frame structure illustrated in FIG. 2.
FIG. 2 illustrates a frame structure for relay service in a wireless communication system according to the conventional art.
As illustrated in FIG. 2, a frame of the relay wireless communication system is composed of a Downlink (DL) subframe 220 and an Uplink (UL) subframe 230. Here, the DL subframe 220 is divided into a DL access zone 222 and a DL relay zone 224, and the UL subframe 230 is divided into a UL access zone 232 and a UL relay zone 234.
A DL subframe 220 of a BS frame 200 is composed of a DL access zone 222 and a DL relay zone 224. During the DL access zone 222, a BS transmits a signal to an MS connected through a direct link. During the DL relay zone 224, the BS transmits a signal to an RS.
A UL subframe 230 of the BS frame 200 is composed of a UL access zone 232 and a UL relay zone 234. During the UL access zone 232, the BS receives a UL signal from the MS. During the UL relay zone 234, the BS receives a UL signal from the RS.
A DL subframe 220 of an RS frame 210 is composed of a DL access zone 222 and a DL relay zone 224. During the DL access zone 222, an RS transmits a signal to an MS connected through a relay link. During the DL relay zone 224, the RS receives a signal from the BS. A Relay-Transmit/Receive Transition Gap (R-TTG) 260 is an Orthogonal Frequency Division Multiplexing (OFDM) symbol overhead for operation transition of the RS that exists between the DL access zone 222 and DL relay zone 224 of the DL subframe 220.
A UL subframe 230 of the RS frame 210 is composed of a UL access zone 232 and a UL relay zone 234. During the UL access zone 232, the RS receives a UL signal from the MS. During the UL relay zone 234, the RS transmits a UL signal to the BS. A Relay-Receive/Transmit Transition Gap (R-RTG) 280 is an OFDM symbol overhead for operation transition of the RS that exists between the UL access zone 232 and UL relay zone 234 of the UL subframe 230.
A Transmit/Receive Transition Gap (TTG) 240 exists between the DL subframe 220 and UL subframe 230 of the BS frame 200. The BS makes the transition from a transmit mode to a receive mode during the TTG 240.
An idle time (Idle_Time) 270 exists between the DL subframe 220 and UL subframe 230 of the RS frame 210. The idle time (Idle_Time) 270 is set for the RS frame 210 to be in synchronization with the BS frame 200. During the idle time (Idle_Time) 270, the RS does not make an operation transition. Also, during the Idle-Time 270, transmission/reception of data does not occur.
When providing a relay service as above, the RS frame 210 includes the overheads (i.e., the R-TTG and the R-RTG) for operation transition within the DL subframe 220 and the UL subframe 230. Thus, there is a problem because the operation transition gaps of the RS frame 210 lead to the degradation of a data transmission efficiency of a system.